It is well known in the art that when a typical computer is turned on, the computer executes a self test program referred to as POST. The program is the BIOS (basic input/output system) that is burned into a ROM chip. The BIOS gives the computer a starter mechanism to run the rest of the software from a floppy disk and/or a hard disk. The BIOS is responsible for booting the computer by providing a basic set of instructions. It performs all the tasks that need to be done at start up time. The BIOS also supplies for the operating system an interface to the underlying hardware of the computer in the form of a library of interrupt handlers.
When the system is powered on, the BIOS performs diagnostics and initializes system components, including the video system. This is commonly referred to as POST. Afterwards, the computer will proceed to its final boot up stage by calling the operating system.
Computer systems are known in prior art that are able to simultaneously operate a plurality of display devices, such as CRT displays and LCD displays. Such computers may have multiple video adapters or may have a dual CRT Controllers graphics card. The multiple displays are used for simultaneously running multiple applications. Under the Windows 98 operating system this concept is known as extended desktop wherein the cursor can drag an icon, file, etc. from the screen of one display device to the screen of another display device. A dual CRT Controllers graphics card is used to operate the two screens of the displays.
Under Windows 98 operating systems, it is possible to operate four displays, which, for example, can be run from a first dual CRT Controller graphics card, and the other two from a second dual CRT Controller graphics card. In this case, the computer system has multiple display adapters. Whatever the configuration, it has become an accepted and desired feature for a computer to have the ability to interface with and operate multiple video adapters for simultaneously running multiple display devices.
With the release of the Windows 2000 operating system and especially in the portable or laptop computer environment, it was found that it was no longer possible to support multiple video adapters if any of the video adapters has compressed Video BIOS. For multiple video cards to operate, it is desirable that all of the Video BIOSs be initialized during POST. However, the Windows 2000 operating system is not capable of doing this. Under the Windows 2000 operating system only the primary video adapter is POSTed. Although this primary video adapter could be a dual CRT Controller graphics card for running two display devices, it is not possible to use an add-on video graphics card with an onboard or built in video adapter. Many motherboards for computers have video adapters built into and stored on the motherboard. That is, the video BIOS is stored in compressed form in a ROM chip on the motherboard.
Portable computers, such as laptops, typically have the video BIOS stored in compressed form on the motherboard. If, however, an add-on video card is used, and if this add-on video card is designated as the primary adapter, the video adapter on the motherboard becomes the secondary video adapter and under the Windows 2000 operating system it is no longer available for use after the POST by the System BIOS.
There is a need for a method and apparatus for executing a POST for each Video BIOS for a computer in which the computer system is capable of operating multiple video adapters. That is, there is a need for operating multiple display devices for multiple displays under the Windows 2000 operating system, especially for laptop computers.